1. Field of the Invention
The invention relates to the field of laminated fabric and processes for producing it. More particularly, the invention is a wind-resistant, breathable laminated fabric and the process for producing it.
2. Description of Related Art
There are a number of different weatherproof, breathable fabrics, some of which are fabric laminates, wherein a weatherproof material can be one that is only windproof, only waterproof, or both windproof and waterproof. The existence of a multitude of weatherproof, breathable fabrics is evidence of the consumer demand for and high utility of such products. Many people who spend a substantial amount of time outside have experienced the discomfort of wearing typical weatherproof, non-breathable clothing. The fabric from which typical weatherproof, non-breathable clothing is manufactured keeps out water and wind, but also keeps in moisture. People naturally perspire and people exerting themselves perspire even more. Accordingly, people exerting themselves while wearing non-breathable clothing will quickly begin to feel the dampness of moisture in their clothing from accumulated perspiration. The dampness increases as the perspiration continues to accumulate causing further discomfort. When people wear weatherproof clothing to keep out water and wind, they often wear clothing to insulate their bodies from the cold in conjunction with the weatherproof clothing. Unfortunately, the effectiveness of most types of insulating materials used in clothing is diminished when moisture accumulates in the clothing. Accordingly, people wearing non-breathable clothing often experience the discomfort of dampness as well as the discomfort of becoming cold. Some of the references disclosing conventional fabrics to overcome such problems include U.S. Pat. No. 5,439,733 issued to Paire, U.S. Pat. No. 4,311,745 issued to Civardi, U.S. Pat. No. 4,147,829 issued to Holland, U.S. Pat. No. 3,855,048 issued to Bagnall, and U.S. Pat. No. 3,410,748 issued to Blue. The indicated references while at least partially successful in providing weatherproof, breathable fabric do not overcome the problems associated with spending time outside.
One of the problems associated with conventional weatherproof, breathable fabric is that its performance is generally inadequate. Performance of a fabric involves several criteria, including how well it inhibits wind and liquid water seepage, how well it permeates water vapor, and how comfortable it is to wear when used in clothing. Conventional weatherproof fabrics claiming to be breathable usually perform quite well at inhibiting wind and liquid water from seeping though the material, but perform rather poorly at permeating water vapor away from the wearer. It is well known that a person who wears the most popular types of weatherproof, breathable fabrics while exerting themselves will quickly accumulate perspiration moisture in their clothing. The most popular of fabrics appear to perform well in breathability only when perspiration rates are low. Also, conventional fabrics are known for being uncomfortable to wear in that they are "boardy" or stiff to the touch. Interestingly, when weatherproof, breathable fabrics first became available, their popularity soared, but that popularity has backlashed to some extent. Many consumers have become so dissatisfied with the lack of performance in the areas of breathability and comfort that they prefer to wear breathable, comfortable fabric and take other measures to protect themselves from wind and water.
The counter trend in consumer demand is also well recognized and attempts have been made to improve the breathability and comfort of fabrics. Solutions have centered upon attempting to change the materials and/or processes used to manufacture weatherproof, breathable fabrics in a manner that yields a more desirable product. Former processes involved laminating a breathable film between an inner and an outer fabric. Such lamination was accomplished by placing adhesive layers in between the three-ply combination, yielding a five-layer fabric laminate comprising an outer fabric, adhesive line, film, adhesive line, and inner fabric. Depending on the specific film and inner and outer fabrics chosen, the final fabric possessed some degree of a weatherproof characteristic and some degree of a breathable characteristic. A central problem of all such fabrics manufactured using this process was that breathability was unsatisfactory and the combination of the film and two fabrics held together with adhesive left the fabric too "boardy" and stiff. The process was additionally undesirable because of its cost. The film was an expensive material to include and there was more risk of processing failure because of multiple processing steps, any one of which could fail and yield a defective product.
Current technology teaches use of polymer foam as a bonding agent between fabrics that allows the bonded fabrics to maintain more of their original flexibility after bonding than the same fabrics bonded with adhesive. A laminate of two supple fabrics bonded together with adhesive will generally be less supple than the two original fabrics, but if polymer foam is used not as much suppleness is lost. Current technology also teaches various methods for effectuating a bond between a polymer foam and fabric so that the foam can act as a bonding agent between two fabric layers. Some methods use a third material, such as adhesive or a thermosetting polymer placed between the foam and fabric to bond them together, but in such cases the polymer foam is really a filler between fabrics rather than a true bonding agent. Methods wherein the foam is a true bonding agent involve applying both heat and pressure to encourage the foam to become embedded in the fibers of the fabric, forming the necessary bond. It is well-known that heating polymer foam by exposing it to a flame and compressing it with heated rollers onto fabric will melt the foam and embed it into the fabric, forming a high-strength bond. This method is typically called foam flame bonding.
Within the foam flame bonding technology, it is also known that if the temperature of the foam is high and the compressive pressure of the foam onto the fabric is high that any suppleness of the original fabric will be reduced. Generally, current technology teaches that a trade-off exists between bond strength and suppleness. The temperatures and pressures applied in foam flame bonding may be reduced to correspondingly reduce the loss of suppleness, but the bond strength will be reduced as a result. Bagnall discloses one method of forming a bond between foam and fabric that attempts to overcome the trade-off by yielding a strong bond without sacrificing fabric suppleness. The Bagnall method involves using a single-pass laminating machine to heat one side of a polyester urethane foam sheet to less than 360.degree. C. with a very weak flame before pressing it against a fabric layer, and then to heat the foam face of the foam-fabric laminate to greater than 400.degree. C. with a fierce flame before pressing it against a second fabric layer. This method apparently yields a fabric with equivalent drape properties to conventional foam laminates, but with greater bond strength. However, the fabric nonetheless lacks a weatherproof and breathable characteristic.
The advancement of the foam flame bonding technology provided a way to bond breathable films to fabrics without sacrificing as much of the suppleness formerly lost by bonding films to fabrics with adhesive. Although such advancements eliminated a portion of the stiffness, some of it remained and the problem of breathability remained as well. Accordingly, current technology does not teach a method for forming a foam flame bonded fabric laminate that is weatherproof, breathable, and supple.
Thus, it can be seen from the above discussion that it would be an improvement in the art to provide a strongly bonded fabric laminate that is weatherproof, breathable, and supple. Specifically, this means providing a foam flame process for manufacturing such fabric that overcomes the disadvantages of the current technology.